Method and apparatus for determining track density during a servo-track writing operation

Abstract

Disk drives are produced having a track density that is determined during a servo-track writing operation. A plurality of calibration tracks is written onto a storage medium of a disk of a head-disk assembly at a calibration track density. The calibration track density corresponds to a portion of a nominal track density profile. An aspect of the servo performance of the head-disk assembly is measured at the calibration tracks. A selected track density profile is identified based on the measured servo performance. The plurality of tracks is written to storage medium at the selected track density profile.

What is claimed is:  
     
       1. A method for manufacturing a disk drive that comprises a head-disk assembly having a disk with a storage medium, the head-disk assembly having a servo performance, the method comprising: 
       writing a plurality of calibration tracks onto the storage medium at a calibration track density profile corresponding to a portion of a nominal track density profile;  
       measuring the servo performance of the head-disk assembly at the calibration tracks;  
       selecting a track density profile based on the measured servo performance of the head-disk assembly; and  
       writing a plurality of tracks to the storage medium of the disk at the selected track density profile.  
     
     
       2. The method of  claim 1 , wherein the average track density of the selected track density profile is greater than the average track density of the nominal track density profile. 
     
     
       3. The method of  claim 1 , wherein the average track density of the selected track density profile is less than the average track density of the nominal track density profile. 
     
     
       4. The method of  claim 1 , wherein the average track density of the selected track density profile is about equal to the average track density of the nominal track density profile. 
     
     
       5. The method of  claim 1 , wherein the median track density of the selected track density profile is greater than the median track density of the nominal track density profile. 
     
     
       6. The method of  claim 1 , wherein the median track density of the selected track density profile is less than the median track density of the nominal track density profile. 
     
     
       7. The method of  claim 1 , wherein the median track density of the selected track density profile is about equal to the median track density of the nominal track density profile. 
     
     
       8. The method of  claim 1 , wherein the step of measuring the servo performance of the head-disk assembly further comprises measuring the position error signal of the head-disk assembly at the calibration tracks. 
     
     
       9. The method of  claim 8 , wherein the measured position error signal of the head-disk assembly at the calibration tracks is higher than a nominal position error signal of a nominal disk drive, and wherein the selected track density profile has an average track density that is less than the average track density of the nominal track density profile. 
     
     
       10. The method of  claim 8 , wherein the measured position error signal of the head-disk assembly at the calibration tracks is lower than the position error signal of a nominal disk drive, and wherein the selected track density profile has an average track density that is not less than the average track density of the nominal track density profile. 
     
     
       11. The method of  claim 1 , wherein the step of measuring the servo performance of the head-disk assembly further comprises measuring the settle time of the head-disk assembly. 
     
     
       12. The method of  claim 11 , wherein the measured settle time of the head-disk assembly is longer than a nominal settle time of a nominal head-disk assembly, and wherein the selected track density profile has an average track density that is less than the average track density of the nominal track density profile. 
     
     
       13. The method of  claim 11 , wherein the measured settle time of the head-disk assembly is shorter than the settle time of a nominal head-disk assembly, and wherein the selected track density profile has an average track density that is not less than the average track density of the nominal track density profile. 
     
     
       14. The method of  claim 11 , wherein the step of measuring the servo performance of the head-disk assembly further comprises measuring the position error signal of the head-disk assembly at the calibration tracks. 
     
     
       15. A method for manufacturing a disk drive that comprises a head-disk assembly having a disk with a storage medium, the head-disk assembly having a servo performance, the method comprising: 
       writing a plurality of calibration tracks onto the storage medium at a calibration track density profile corresponding to a portion of a nominal track density profile;  
       measuring the position error signal of the head-disk assembly and the settle time of the head-disk assembly at the calibration tracks;  
       identifying a density-based track density profile based on the measured position error signal of the head-disk assembly;  
       determining whether the value of the measured position error signal permits reducing the average density of the density-based track density profile in order to improve the settle time of the head-disk assembly;  
       selecting a track density profile based on the determining step; and  
       writing a plurality of tracks to the storage medium of the disk at the selected track density profile.  
     
     
       16. The method of  claim 15 , wherein the measured position error signal of the head-disk assembly is low, the measured seek performance of head-disk assembly is high, and the average track density of the selected track density profile is greater than the average track density of the nominal track density profile. 
     
     
       17. The method of  claim 15 , wherein the position error signal of the head-disk assembly is high, the seek performance of head-disk assembly is high, and the average track density of the selected track density profile is less than the average track density of the nominal track density profile. 
     
     
       18. The method of  claim 15 , wherein the position error signal of the head-disk assembly is low, the seek performance of head-disk assembly is low, and the average track density of the selected track density profile is greater than the average track density of the nominal track density profile. 
     
     
       19. A servo-track writer for writing a plurality of calibration tracks on a storage medium of a head-disk assembly at a calibration stepping increment and for writing a plurality of servo-tracks on the storage medium of the head-disk assembly at a selected stepping increment, the head-disk assembly comprising a read element, a write element, and an actuator, the head-disk assembly having a servo performance, the servo-track writer comprising: 
       (a) a controller that processes a clock reference pattern to determine the circumferential location of the write element and that directs the write element to write the servo-tracks to the storage medium;  
       (b) a servo performance measurement circuit that measures an aspect of the servo performance of the head-disk assembly and that selects a stepping increment based thereon; and  
       (c) a head positioner circuit that comprises a positioning mechanism that imparts a step-wise movement to the actuator at a calibration stepping increment for writing the plurality of calibration tracks, and that imparts a step-wise movement to the actuator at the selected stepping increment for writing the plurality of servo-tracks to the storage medium.  
     
     
       20. The servo-track writer of  claim 19 , wherein the selected stepping increment is greater than the calibration stepping increment. 
     
     
       21. The servo-track writer of  claim 19 , wherein the selected stepping increment is less than the calibration stepping increment. 
     
     
       22. The servo-track writer of  claim 19 , wherein the servo performance measurement circuit is capable of measuring the position error signal of the head-disk assembly at the calibration tracks. 
     
     
       23. The servo-track writer of  claim 19 , wherein the servo performance measurement circuit is capable of measuring the settle time of the head-disk assembly. 
     
     
       24. The servo-track writer of  claim 23 , wherein servo performance measurement circuit is capable of measuring the position error signal of the head-disk assembly at the calibration tracks. 
     
     
       25. A disk drive comprising: 
       a head-disk assembly having a servo performance, the head disk assembly comprising:  
       an actuator;  
       a read element;  
       a write element;  
       a spindle motor; and  
       a disk having a storage medium, the disk mounted on the spindle motor, the storage medium written by:  
       writing a plurality of calibration tracks onto the storage medium at a calibration track density corresponding to a portion of a nominal track density profile;  
       measuring the servo performance of the head-disk assembly at the calibration tracks;  
       selecting a track density profile based on the measured servo performance of the head-disk assembly; and  
       writing a plurality of servo-tracks to storage medium of the disk at the selected track density profile.  
     
     
       26. The disk drive of  claim 25 , wherein the average track density of the selected track density profile is greater than the average track density of the nominal track density profile. 
     
     
       27. The disk drive of  claim 25 , wherein the average track density of the selected track density profile is less than the average track density of the nominal track density profile. 
     
     
       28. The disk drive of  claim 25 , wherein the step of measuring the servo performance of the head-disk assembly further comprises measuring the position error signal of the head-disk assembly at the calibration tracks. 
     
     
       29. The disk drive of  claim 25 , wherein the step of measuring the servo performance of the head-disk assembly further comprises measuring the settle time of the head-disk assembly. 
     
     
       30. The disk drive of  claim 29 , wherein the step of measuring the servo performance of the head-disk assembly further comprises measuring the position error signal of the head-disk assembly at the calibration tracks. 
     
     
       31. A disk drive comprising: 
       a head-disk assembly having a servo performance, the head disk assembly comprising:  
       an actuator;  
       a read element;  
       a write element;  
       a spindle motor; and  
       a disk having a storage medium, the disk mounted on the spindle motor, the storage medium written by:  
       writing a plurality of calibration tracks onto the storage medium at a calibration track density corresponding to a portion of a nominal track density profile;  
       measuring the position error signal and the settle time of the head-disk assembly at the calibration tracks;  
       identifying a density-based track density profile based on the measured position error signal of the head-disk assembly;  
       determining whether the value of the measured position error signal permits reducing the average density of the density-based track density profile in order to improve the settle time of the head-disk assembly;  
       selecting a track density profile based on the determining step; and  
       writing a plurality of servo-tracks to the storage medium of the disk at the selected track density profile.  
     
     
       32. The disk drive of  claim 31 , wherein the measured position error signal of the head-disk assembly is low, the measured seek performance of head-disk assembly is high, and the average track density of the selected track density profile is greater than the average track density of the nominal track density profile. 
     
     
       33. The disk drive of  claim 31 , wherein the position error signal of the head-disk assembly is high, the seek performance of head-disk assembly is high, and the average track density of the selected track density profile is less than the average track density of the nominal track density profile. 
     
     
       34. The disk drive of  claim 31 , wherein the position error signal of the head-disk assembly is low, the seek performance of head-disk assembly is low, and the average track density of the selected track density profile is greater than the average track density of the nominal track density profile.